1. Field of the Invention
This invention relates to a compositions of matter useful in performing extracapsular cataract operations and to a method of performing such operations with the use of such compositions. More particularly, the invention relates to the use of a solution of alpha-chymotrypsin in the area of operative treatment of grey cataract.
2. Description of the Prior Art
Grey cataract is an ailment of the eye in which there develops a darkening or clouding of the lens and a decrease of vision produced thereby. By the so called intra-capsular operation, the darkened or clouded lens, which is located in a capsule, is removed by extraction as a whole together with the capsule.
By another method, the so-called extracapsular operation, which is widely used nowadays, the darkened or clouded lens is likewise removed, but the posterior capsule is left behind. Then one proceeds as follows: next, the anterior capsule of the lens is removed. Next, the main part of the lens and the intracapsular posterior rind coating are drawn away with the aid of a flushing process with simultaneous irrigation. There exists also the possibility of using an ultrasonic sound apparatus for the destruction of the main body of the lens and its removal by aspiration. The objective of this operation is to obtain the posterior capsule, in order that a clear division can be maintained between glass body and anterior chamber and to that extent to keep physiological properties or the same. In most cases, there is practiced in such operations the implantation of a posterior chamber lens which replaces the removed darkened or clouded lens. A prerequisite for this is that the posterior capsule is obtained by the operation and that the capsule is completely clear. It is known to mechanically polish the posterior capsule before the implantation of the posterior chamber lens. Despite careful polishing, there frequently develops a so-called capsule fibrosity; this concerns a thickening of the capsule because of very fine particles which cannot be seen microscopically during the operation and form a thickened film on the capsule.
Alpha-chymotrypsin is a substance that in the cleanest, crystallized, dialyzed and stabilized form is obtainable in commerce. The molecular weight is 22,500; the isoelectric point lies between a pH value of 5 to 4; and the effective maximum is at 8.1 to 8.6.
The use of alpha-chymotrypsin is known for the practice of intracapsular operations. There the substance is used in the dilution of 1:5,000 to 1:10,000 and it serves for enzymatic zonulolysis, that is, the dissolution of the zonule fibers that hold the lens in tension. It was therefore surprising to establish, and not foreseeable, that the same substance could be used in a dilution of 1:20,000 to 1:30,000 under conditions that the fibers are not dissolved and the solution can be used for the cleaning of the posterior capsule.